1. Technical Field
The present invention relates to powder metallurgy, injection-molded infiltrated precision articles, such as reaction engine or rocket nozzles, and rocket thrust chambers produced without machining or other mechanical shaping operations, and a process for forming said articles.
2. Background Art
Powdered metallurgy techniques have been used to produce infiltrated refractory metal articles having superior erosion and high-temperature resistance. Infiltrated articles are articles in which porosity in a body has been filled by a second phase. The second phase may be deposited in interconnected porosity of the first phase through melting, flowing in under pressure, or under capillary forces, and then solidifying, or it may be deposited by other means such as chemical vapor deposition.
A wear-resistant sintered alloy product is produced according to one method by mixing powders of an alloy, tungsten, and optional metals such as nickel. This mixture is packed in a mold to form a green product and sintered. Sintering the mixture forms a sintered product with a pearlite matrix microstructure. The sintered product is then infiltrated with either molten copper or a molten copper alloy to produce an infiltrated sintered product.
Another conventional method produces bodies composed of a refractory metal containing material as the major constituent, and an alloy matrix of a refractory metal in a metal or metals such as iron, nickel, copper, cobalt and chromium. The article or body is prepared by forming a porous sintered skeleton of refractory metal containing material, filling voids of the skeleton with a molten alloy containing a refractory metal, and then solidifying the molten alloy to provide the desired body.
The conventional methods for production of a complex-shaped infiltrated metal article of manufacture suffer from several disadvantages. One disadvantage encountered is the problem of shrinkage during the sintering of the article.
Also, in the case where a metal or metal alloy is infiltrated into a sintered skeleton or article, production of complex shapes is difficult or impossible because machining of the very hard and brittle material is difficult and expensive. A net or near-net shape process, such as injection molding, is needed for producing high quality sintered articles absent the aforementioned deficiencies.